Secondary pulmonary alveolar proteinosis (PAP) has been described in several clinical settings that can be grouped into three main categories: infections of the lung; haematological malignancies and other conditions that alter the patient's immune status; and exposure to inhaled chemicals and minerals. Recent studies reported that anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibody was present in the serum of patients with idiopathic PAP but not in patients with secondary PAP or in normal subjects. The present report describes the interesting case of a patient with Behcet's disease and PAP. The absence of anti-GM-CSF antibodies in this patient suggested a diagnosis of secondary PAP.